Immunotherapy (desensitization; hyposensitization) has been used in the treatment of atopic diseases for over 50 years. Controlled studies in ragweed hayfever have been extensive, but definitive studies are badly needed in bronchial asthma with particular reference to allergens such as house dust and mold. A large number of patients with allergic bronchial asthma are cared for at the University of Iowa and the addition of Dr. Metzger to our staff is viewed as an opportunity for maximum utilization of the Clinical Research Center in coordinating clinical and laboratory studies of atopic patients. Investigations will include provocative bronchial challenge (with particular interest in late responses), measurement of specific secretory IgA antibodies against inhalant allergens, specific IgE levels, specific "blocking" IgG antibody levels, histamine release and studies of suppressor cell activities in patients with allergic bronchial asthma. Differences in these responses will be analyzed between atopic symptomatic and asymptomatic patients and between patients who have and those who have not been treated successfully with immunotherapy. These investigations are expected to yield new and important information on the clinical value and basic mechanisms of immunotherapy in atopic disease.